I have a question regarding the effect of source address affinity persistence. Will it also over rule the resolution of GTM given to client for a URL?

We have a GTM pointing to two virtual servers in its wide ip, these are the virutal serves existing on our LTMs( on in each of the two data centers), and these virtual servers in turn have the forward proxies as their pool members. Lately we were seeing high proxy utilization on one of the data center proxies. We have checked that the GTM is doing its resolution normally ( round robin ) as expected to these virutal servers. But when i check the number of connections on the virutal servers i can see that the number of connections on one of the virtual servers is almost double the other virtual servers connections in other datacenters LTM. Both of these virtual servers have Source address affinity as their persistence profile. Any explaination of why this behavious is occuring ?